NED Abstract

Copyright by American Astronomical Society.
Reproduced by permission
2009ApJ...704..324R
Less Than 10 Percent of Star Formation in z ~ 0.6 Massive Galaxies is
Triggered by Major Interactions
Robaina, Aday R.; Bell, Eric F.; Skelton, Rosalind E.; Mc Intosh, Daniel
H.; Somerville, Rachel S.; Zheng, Xianzhong; Rix, Hans-Walter; Bacon,
David; Balogh, Michael; Barazza, Fabio D.; Barden, Marco; Bohm, Asmus;
Caldwell, John A. R.; Gallazzi, Anna; Gray, Meghan E.; Haussler, Boris;
Heymans, Catherine; Jahnke, Knud; Jogee, Shardha; van Kampen, Eelco; Lane,
Kyle; Meisenheimer, Klaus; Papovich, Casey; Peng, Chien Y.; Sanchez,
Sebastian F.; Skibba, Ramin; Taylor, Andy; Wisotzki, Lutz; Wolf, Christian
Abstract. Both observations and simulations show that major tidal
interactions or mergers between gas-rich galaxies can lead to intense
bursts of star formation. Yet, the average enhancement in star formation
rate (SFR) in major mergers and the contribution of such events to the
cosmic SFR are not well estimated. Here we use photometric redshifts,
stellar masses, and UV SFRs from COMBO-17, 24 micron SFRs from Spitzer,
and morphologies from two deep Hubble Space Telescope (HST) cosmological
survey fields (ECDFS/GEMS and A901/STAGES) to study the enhancement in SFR
as a function of projected galaxy separation. We apply two-point projected
correlation function techniques, which we augment with morphologically
selected very close pairs (separation <2") and merger remnants from the
HST imaging. Our analysis confirms that the most intensely star-forming
systems are indeed interacting or merging. Yet, for massive (M_*_ >=
10^10^ M_sun_) star-forming galaxies at 0.4 < z < 0.8, we find that the
SFRs of galaxies undergoing a major interaction (mass ratios <=1:4 and
separations <=40 kpc) are only 1.80 +/- 0.30 times higher than the SFRs of
non-interacting galaxies when averaged over all interactions and all
stages of the interaction, in good agreement with other observational
works. Our results also agree with hydrodynamical simulations of galaxy
interactions, which produce some mergers with large bursts of star
formation on ~100 Myr timescales, but only a modest SFR enhancement when
averaged over the entire merger timescale. We demonstrate that these
results imply that only <~10% of star formation at 0.4 <= z <= 0.8 is
triggered directly by major mergers and interactions; these events are not
important factors in the build-up of stellar mass since z = 1.
Key words: galaxies: evolution, galaxies: general, galaxies: interactions,
galaxies: starburst, galaxies: statistics, infrared: galaxies